<?php
defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * Class Captcha
 * 验证码生成类
 */

class Captcha
{
    /**
     * @var CI_Controller
     */
    protected $CI;

    /**
     * 验证码 session 索引
     * @var string
     */
    public $session_name = 'captcha_code';

    public function __construct()
    {
        $this->CI =& get_instance();
        $this->CI->load->library('session');
    }

    public function get_code($num, $w, $h)
    {
        $code = "";
        for ($i = 0; $i < $num; $i++) {
            $code .= rand(0, 9);
        }
        //将生成的验证码写入session
        $this->CI->session->set_userdata($this->session_name, $code);
        //创建图片 定义颜色值
        Header("Content-type: image/PNG");
        $im = imagecreate($w, $h);
        $black = imagecolorallocate($im, 47, 82, 144);
        $gray = imagecolorallocate($im, 255, 255, 255);
        $bgcolor = imagecolorallocate($im, 255, 255, 255);

        imagefill($im, 0, 0, $gray);

        //画边框
        imagerectangle($im, 0, 0, $w - 1, $h - 1, $black);

        //随机绘制两条虚线 起干扰作用
        $style = array(
            $black,
            $black,
            $black,
            $black,
            $black,
            $gray,
            $gray,
            $gray,
            $gray,
            $gray
        );
        imagesetstyle($im, $style);
        $y1 = rand(0, $h);
        $y2 = rand(0, $h);
        $y3 = rand(0, $h);
        $y4 = rand(0, $h);
        imageline($im, 0, $y1, $w, $y3, IMG_COLOR_STYLED);
        imageline($im, 0, $y2, $w, $y4, IMG_COLOR_STYLED);

        //在画布上随机生成大量黑点 起干扰作用;
        for ($i = 0; $i < 70; $i++) {
            imagesetpixel($im, rand(0, $w), rand(0, $h), $black);
        }
        //将数字随机显示在画布上 字符的水平间距和位置都按一定波动范围随机生成
        $strx = rand(3, 8);
        for ($i = 0; $i < $num; $i++) {
            $strpos = rand(1, 6);
            imagestring($im, 5, $strx, $strpos, substr($code, $i, 1), $black);
            $strx += rand(8, 12);
        }
        imagepng($im);
        imagedestroy($im);
    }
}